1. Field of the Invention
The present invention relates to a display configuration setting system suitable for a computer system such as a personal computer or a personal workstation which comprises a plasma display as standard equipment, and can optionally connect a CRT (Cathode Ray Tube).
2. Description of the Related Art
Along with rapid advances of microprocessors, various personal computers, personal workstations, and the like have been developed. Some of these computers have a display configuration in which a plasma display is equipped as standard equipment, and a CRT display can be optionally connected. Such a computer incorporates display hardware controllers respectively for the plasma display and the CRT display. A VGA (Video Graphic Adapter) is a typical CRT display hardware controller.
Furthermore, with recent advances of display control techniques, more advanced display hardware controllers, e.g., an EGA (Enhanced Graphic Adapter), CGA (Color Graphic Adaper), and the like have been developed. In order to allow use of such display hardware controllers, an extension slot is formed in a computer main body, and the EGA or CGA is inserted in the extension slot as an optional display hardware controller board.
However, upon setting of the display configuration, if a certain type of adapter board (e.g., the EGA) is inserted in the extension slot while the display configuration for using the incorporated display hardware controller (e.g., the VGA) is set, two display control hardware elements which interfere with each other are connected on a system bus, and a normal display control operation cannot be executed.
More specifically, each of the VGA and EGA has a video memory. For this reason, two video memories assigned to one address space are present. In the data read mode, a block is read out onto the system bus from each controller video memory, and correct data cannot be obtained.